Radioluminescent, thermoluminescent and dosimetric properties of X-ray phosphors

Abstract

IntroductionThe study is devoted to visualization and detection of high-level, high-energy and high dose rate ionizing radiation created by isotopes of Chernobyl accident, that are still present inside Chernobyl Shelter. Our approach in solving the problem of visualization was to apply the X-ray phosphors widely used for intensifying luminescent screens or in computed tomography [1,2] and to test their emitting properties under high-energy and high-dose conditions.Here we report on spectral (RL, TL) and dosimetric properties of X-ray phosphors, which displayed high efficiency in converting the ionizing radiation into visible luminescence [3,4]. ExperimentalMaterials: Samples of Eu-containing phosphors such as BaFCl:Eu, Sr 3 (PO 4 ) 2 :Eu, Y 2 Î 3 :Eu and ZnS.CdS:Ag have been studied. Europium and argentum doped polycrystalline powders were obtained by the conventional solid state reaction; concentration of Eu and Ag was near 0.5 mol% in all samples.For the investigation the following techniques were used:1. Time-resolved radioluminescence (RL). Excitation was induced by high-energy (4Mev) electron pulses of linear electron accelerator (LINAC) with ~ 2.6 ms duration and ~ 100 Gy dose, time resolution 1ms. An optical system consisting of lenses, fiber optic bundels, grating monochromator and a photomultiplier tube was applied as light detecting system; a digital storage scope stored the signal as the function of time (Fig.1).2. Thermoluminescence (TL). 3-D TL spectra measurements were carried out using spectrometer, described in [5]. TL glow curves dose -dependence measurments were performed as in [6]. ResultsRadioluminescence and dosimetric properties in high dose rate region.The study of time-resolved RL induced by high-energy (4 MeV) accelerated electrons provides information Kn, Ya Abstract. Time-resolved radioluminescence (RL) of X-ray phosphors: BaFCl:Eu, ZnS.CdS:Ag and Y 2 Î 3 :Åu, which exhibited ultraviolet (λ max = 390 nm), yellow-green, (λ max = 530 nm) and red (λ max =620 nm) luminescence respectively, have been measured. For tested phosphors a good proportionality between the light output of the radioluminescence and the dose rate in the region of dose rates from 3 to 45 MGy/s has been obtained. It was also revealed that the emitting properties of all phosphors are preserved after high-dose (10 4 Gy) and high temperature (500°C) annealing the samples. Thermoluminescent (TL) characterization of Sr 3 (PO 4 ) 2 :Eu and BaFCl:Eu under X-ray, beta and gamma irradiation have been performed. Linear TL dose dependence under irradiation dose in the mGy -Gy region was revealed, which makes these phosphors suitable also for luminescence dosimetry in the low doses region. Thus, the main characteristics of phosphors: i) the high conversion efficiency, ii) the good dose-rate proportionality, iii) the radiation stability allow to consider these materials as promising for high-energy and high dose rate dosimetry.